Inorganic free-radical initiators such as metal or ammonium salts of persulfate or other water soluble initiators such as redox systems are commonly employed in both aqueous solution, dispersion or emulsion polymerization of vinyl monomers. These inorganic initiators are relatively inexpensive and do not produce undesirable decomposition products compared with organic initiators commonly employed in vinyl free-radical polymerization.
Due to their insolubility in organic solvents such as alcohols, ketones, esters, hydrocarbons, etc., these water soluble initiators can not be used in such non-aqueous homogeneous (solution) polymerization processes. Non-aqueous solution free-radical polymerizations are therefore carried out with organic solvent soluble initiators such as peroxy esters of organic acids or organic azo initiators. The use of these initiators is often undesirable since the decomposition and reaction products of the organic initiators are toxic and/or cause undesirable odor in the final product which are used in personal products such as cosmetics.